Theshed
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| posted on 20/1/13 at 11:47 AM |
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Couple of Damper questions
Shed a bit cold this weekend so I thought I would rebuild my front dampers. I bought 4 secondhand Penske units some time ago. I did not notice quite
what a bargain they were. They are 4 way adjustable and owner rebuildable. In fact they come apart with a pin wrench and a couple of spanners.
 
Shocks
 
Shocks
Two out of the 4 I bought had identical shims and pistons so I have built them up using the best bits. All good fun but I have some questions for the
experts....
(1) I have no starting point whatsoever for valving so am I right in thinking that as a very rough start a higher spring rate will need stiffer shims
to keep it under control?
(2) Refilling the shocks with oil looks messy but not over complicated. The Nitrogen is more of an issue. I could rent a bottle from BOC but does
anybody know of a friendly person with a regulator (200psi) who would help with this bit without insisting on doing a service?
(3) last question is where can I find anybody selling clips like the photo below...my googling skills have failed me....what is the common name?
 
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rusty nuts
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| posted on 20/1/13 at 12:13 PM |
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Can't help with question 1 but you may find some tyre companies have nitrogen gas and the correct regulator??
The clips look like wire circlips
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Acc8braman
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| posted on 20/1/13 at 12:14 PM |
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Hi,
Is it some sort of Circlip?
Can you google shock absorber circlip
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phelpsa
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| posted on 20/1/13 at 12:47 PM |
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I'd just fill them with air while you're testing. The temperatures you'll probably be looking at, I doubt it will make any
difference.
I would stick 120psi of moisture free air (compressor with moisture trap) in until I know i wouldn't have to take them apart regularly. 200psi
sounds a bit excessive anyway.
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Theshed
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| posted on 20/1/13 at 01:12 PM |
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Many thanks guys - you are right filling with air - which is after all 79% nitrogen seems like the go
As for the circlips all googling has failed to find any retail source...
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Dunbikin
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| posted on 20/1/13 at 01:20 PM |
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Hi try these guys
http://www.springmasters.com/circlips.html
The clips are called snap rings
Ron said it would cost 250 quid. My wife thinks it did.
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MikeCapon
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| posted on 20/1/13 at 02:54 PM |
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Hi,
Best of luck building your shocks.
1 Heavier springs will require more damping so more/thicker shims.
2 I have never used air instead of nitrogen. I'd be concerned about strapping four potential bombs to my car to be honest. The reason nitrogen
is ued is because it is inert. 200 psi is high but not unreasonable. 10 bar is a widely used pressure but the ideal pressure will depend on stroke,
spring rate and what you are using the shocks for.
3 You need some Round Wire Snap Rings. Google will help you here.
www.shock-factory.co.uk
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phelpsa
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| posted on 20/1/13 at 03:06 PM |
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quote:
Originally posted by MikeCapon
Hi,
Best of luck building your shocks.
1 Heavier springs will require more damping so more/thicker shims.
2 I have never used air instead of nitrogen. I'd be concerned about strapping four potential bombs to my car to be honest. The reason nitrogen
is ued is because it is inert. 200 psi is high but not unreasonable. 10 bar is a widely used pressure but the ideal pressure will depend on stroke,
spring rate and what you are using the shocks for.
3 You need some Round Wire Snap Rings. Google will help you here.
These are sealed canisters are they not? The oil and air are separated by a piston and never come into contact with each other, so definitely no
potential bombs.
The only reason to use nitrogen in this application is that it is more temperature stable. As I said, you won't be seeing damper temperatures
anywhere near the danger zone.
10bar is what I've always seen, 120psi (8 bar) can be had from a standard compressor, hence the suggestion 
[Edited on 20-1-13 by phelpsa]
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Theshed
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| posted on 20/1/13 at 03:16 PM |
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Hi all
many thanks for the advice - spring clip thingies now purchased minimum order of 24 so I have a spare or...20 if anybody needs one
The 200psi figure is the starting point recommended in the Penske owners manual - the reservoirs are marked max 300psi. There is a separator piston
between the oil and gas.
I have used a shim pack half way up the range to control 600-700 lb/inch springs. We shall see once this thing finally turns a wheel.....
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me!
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| posted on 20/1/13 at 08:27 PM |
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As said, I suggest you try and find some nitrogen. It is used to stop you combusting any oil mist that may be present, same as in gas struts and the
like (where temperature definitely isn't a concern, e.g. office chair!)
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